Sort your products by revenue and you'll get a list. It might even be a useful list. But it's not the list you should be making decisions from.
Revenue rankings tell you what customers are buying. They don't tell you what's actually making you money. A product that generates $50,000 in revenue but costs $48,000 to source, ship, and return is a worse product than one that generates $12,000 with $3,000 in total costs. The first product looks like a winner on your dashboard. The second one actually is.
Most merchants never get past the revenue view. That's how products that quietly drain profit survive in your catalog for months — sometimes years — without anyone noticing.
Why top-selling does not mean top-performing
The gap between "best seller" and "best performer" is often enormous. Here's a real-world scenario that plays out in stores constantly:
Product A — Your top seller
- Revenue: $42,000/month
- Cost of goods: $29,400 (70% COGS)
- Return rate: 18%
- Average discount applied: 12%
- Net margin after returns and discounts: $1,764/month
Product B — Ranked #14 by revenue
- Revenue: $8,500/month
- Cost of goods: $3,400 (40% COGS)
- Return rate: 3%
- Average discount applied: 0%
- Net margin after returns and discounts: $4,947/month
Product B generates nearly three times the profit on a fifth of the revenue. If you're allocating marketing budget, inventory space, or homepage real estate based on revenue alone, you're promoting the wrong product.
The metrics that actually matter
Revenue is one input. Here are the others you need to build a complete picture of product performance.
Margin per unit
Not gross margin percentage — margin per unit in actual currency. A product with a 60% margin on a $10 item gives you $6. A product with a 30% margin on a $200 item gives you $60. Percentages can mislead. Absolute margin per unit tells you what each sale actually contributes.
Calculate it as: (Selling price - COGS - average discount - allocated shipping cost) per unit sold
Sell-through rate
Sell-through rate measures how quickly inventory moves: (Units sold / Units received) x 100 over a given period.
A healthy sell-through rate varies by category, but generally:
- Above 80% in a season — strong performer, consider increasing order quantities
- 50-80% — acceptable, monitor closely
- Below 50% — slow mover, likely headed for markdowns
Products with low sell-through rates tie up capital. Every unit sitting in your warehouse is money that could be working elsewhere.
Return rate by SKU
Aggregate return rates are nearly useless. You need return rates at the SKU level. A store-wide return rate of 8% might mask a product with a 35% return rate that's dragging everything else down.
Track returns as: (Units returned / Units sold) x 100 per SKU
More importantly, track the reason for returns. "Didn't fit" means your sizing guide needs work. "Not as described" means your product listing is misleading. "Defective" means you have a quality problem with that supplier.
Days of supply
Days of supply tells you how long your current inventory will last at the current sell rate: (Current inventory / Average daily unit sales)
This metric bridges product performance and inventory management. A product with 180 days of supply and declining sales velocity is a markdown candidate. A product with 12 days of supply and stable demand needs a reorder yesterday.
Contribution margin
This is the metric that ties everything together. Contribution margin accounts for all variable costs associated with a product — not just COGS, but shipping costs, payment processing fees, return handling costs, and customer service costs attributable to that product.
Contribution margin = Revenue - COGS - shipping - payment fees - return costs - CS costs
This is the truest measure of what a product actually contributes to your bottom line.
Building a product performance scorecard
A scorecard gives every product a composite score across multiple dimensions, so you're not over-indexing on any single metric. Here's a framework you can implement:
| Metric | Weight | Scoring |
|---|---|---|
| Contribution margin per unit | 30% | Top quartile = 10, Bottom = 2 |
| Sell-through rate | 20% | Above 80% = 10, Below 40% = 2 |
| Return rate | 20% | Below 5% = 10, Above 20% = 2 |
| Days of supply | 15% | 15-45 days = 10, Above 120 = 2 |
| Revenue growth trend | 15% | Growing = 10, Declining = 2 |
Multiply each score by its weight and sum them. The result is a single number that represents true product performance. Sort by this composite score instead of revenue, and your product ranking will look very different.
You don't need to get the weights perfect on your first attempt. The point is to shift from a single-metric view to a multi-dimensional one. Adjust the weights based on what matters most to your business — a cash-constrained business might weight days of supply higher, while a brand focused on customer experience might weight return rate higher.
Finding hidden gems and hidden drains
Once you have scorecards, two categories of products emerge that revenue rankings would never surface.
Hidden gems
These are products with modest revenue but outstanding performance across other metrics: high margins, low return rates, fast sell-through, minimal customer service burden. They're profitable, they're efficient, and they're being ignored.
Hidden gems deserve more visibility. Put them in email campaigns. Give them homepage placement. Test paid ads against them. Because they convert well and return infrequently, scaling them up tends to scale profit proportionally — unlike high-revenue products where scaling often means more discounting and more returns.
Hidden drains
These are products that look fine on a revenue chart but are quietly destroying margin. They share common traits:
- High return rates that eat into gross profit
- Heavy discount dependency — they rarely sell at full price
- High customer service ticket rates (sizing questions, complaints, "where's my order")
- Slow sell-through requiring eventual markdowns
- Low or negative contribution margin once all costs are allocated
Hidden drains need intervention. Sometimes that means fixing the product listing to set better expectations (reducing returns). Sometimes it means renegotiating supplier costs. Sometimes it means discontinuing the product entirely and reallocating that inventory budget to your hidden gems.
Rebalancing promotions based on true performance
Most merchants promote their best sellers. This feels intuitive but is often backwards.
Your best sellers already have momentum. They already have reviews, search rankings, and organic traffic. Promoting them further often means discounting products that would have sold at full price — cannibalizing your own margin.
Instead, consider this approach:
Promote products with high scorecard ratings but low visibility. These are your hidden gems. They perform well when customers find them, but customers aren't finding them often enough. Promotion dollars here create incremental revenue rather than subsidizing existing sales.
Stop promoting products with low scorecard ratings but high revenue. If a product is already selling well but has thin margins and high returns, promoting it just amplifies the problem. Let it sell on its own momentum while you fix the underlying issues.
Use scorecard data to set promotional discount ceilings. A product with a $30 contribution margin can absorb a 15% discount and still be profitable. A product with a $4 contribution margin cannot. Set maximum discount percentages per product based on contribution margin, not revenue.
Putting this into practice
Building a product performance scorecard manually is possible but tedious. You need to pull data from multiple sources — sales data, inventory levels, return records, cost data — and combine them into a single view.
Tools like Spark by MishiPay can automate this by connecting to your store platform and calculating multi-dimensional product performance metrics across your entire catalog. Instead of building spreadsheets, you can ask questions like "which products have the highest return rates but lowest margins" or "show me products with declining sell-through rates" and get immediate, data-backed answers.
Whether you automate it or do it manually, the critical shift is the same: stop treating revenue as the definitive measure of product performance. Revenue is the starting point. Margin, sell-through, returns, and contribution are where the real decisions get made.
Start with your top 20 products by revenue. Calculate contribution margin for each. The gap between the revenue ranking and the profit ranking will tell you everything you need to know about where to focus next.
See which products actually drive profit
Spark analyzes your full catalog across margin, sell-through, returns, and more — so you can promote what works and fix what doesn't.